Conventional lighting apparatuses are disclosed in, for example, Japanese Unexamined Patent Application Publication No. 2007-141735 (hereinafter, referred to as “PL 1”), Japanese Unexamined Patent Application Publication No. 2007-80531 (hereinafter, referred to as “PL 2”) and Japanese Unexamined Patent Application Publication No. 1996(H08)-160892 (hereinafter, referred to as “PL 3”).
PL 1 discloses a double-sided light-emitting panel including a light guide plate having a plurality of plasma lamps arranged on end side surfaces thereof, transparent acrylic plates disposed on both surfaces of the light guide plate, and advertising media disposed on the acrylic plates. For the light guide plate, a very clear transparent substrate is used that is made of polymethylmethacrylate, (meth) acrylic acid ester copolymer, polycarbonate, polystyrene, polyvinyl chloride or glass, with a light-diffusing material, such as a transparent or white pigment, mixed in the substrate material.
PL 2 discloses an LED lighting fixture including a light guide plate having an incident surface on one side thereof and an LED arranged so that the direction that the a light-emitting surface faces roughly intersects with the direction that the incident surface faces. This light guide plate is made of a light-transmissive material, such as glass and acrylic.
PL 3 discloses a structure including a light guide plate, which is a light-transmissive plate made of acrylic resin or the like, LEDs arranged on one side of the light guide plate, and dot-patterned light-emitting layers that are provided on surfaces of the light guide plate and emit light outward at an increasing rate while increasing the distance from the LEDs. In the structure, light from the LEDs is once uniformly applied over the entire pattern display portion of the light guide plate and then unnecessary light for the patterns of characters and design depicted on the pattern filter on the light-emitting layer returns into the light guide plate to allow the required characters and design to emerge on the surface.